142 , Proceedings of the Royal Physical Society. 
in order to make observations the breeding- or feeding-ground of the beetle 
must be disturbed by removing the bark from stumps or roots, and this, 
together with the removal of the soil from them, practically prevents 
continuous observation on any pair or group of beetles. This difficulty is 
common to the study of all the Scolytide, but it is increased in the 
case of H. ater (and also in the case of H. cunicularius) by the under- 
ground habitat. There are no means of getting over this difficulty, but where 
- examination of a number of beetles out of the many infesting a given stump 
show these to be uniform as regards sex maturity, and where they are all 
engaged in making brood-galleries, it is permissible to assume that their 
individual behaviour and progress are alike. I believe I have satisfactory 
proof of this as the result of a comparison of the behaviour of three 
individuals in the laboratory with others in the field. On 7th October 1915, 
I obtained at Eddleston several H. ater adults feeding in a young plantation. 
I removed a young pine containing three of these, and kept it in the 
laboratory throughout the winter. The three beetles remained on the pine, 
where I observed them on Sth April. On 6th April, I again visited 
Eddleston, and again found H. ater adults feeding on the pines. It is 
perfectly safe then to assume that those in the field, lke those in the 
laboratory, have fed on the pines all winter. Further evidence of this was 
supplied by the state of the female reproductive organs of the beetles. 
On 7th October, I examined five beetles taken at Eddleston, four were 
females and immature. On 6th April, I examined four beetles, of which 
two were females just arrived at maturity. My observations and notes, 
therefore, form a fairly reliable account of the life-history. 
In view of the fact that my notes refer only to the stage in the meta- 
morphosis and to the habitat of the beetles, which involves considerable 
repetition, I have summarised them as far as they relate to the life-history 
in the table given below. Immediately following is a summary of my notes 
on the habits of H. ater, the nature of its breeding- and feeding-grounds 
and of the insects commonly associated with it. 
A word may be said here on distribution. Hylasies ater is widely 
distributed in Scotland, and it is probable that it is on the increase at 
present owing to the extension of felled areas caused by the drain on our 
timber resources. | 
Breeding-ground.—The favourite and usual breeding-ground of H. ater 
is the Scots pine clearing. It also occurs on the roots of standing dead and 
sickly pines in high forests. Unlike #. palliatus, Myelophilus piniperda, and 
others among the Scolytids, it restricts itself, except in rare instances, to the | 
roots and stumps below the soil level. It was twice found on a larch stump 
